This invention relates to a tuning machine for stringed musical instruments and particularly to a tuning machine which relies primarily on clamping the end of each string rather than relying on the friction of the string wound in multiple loops around the tuning peg or post.
In guitars and other stringed musical instruments, strings of different thickness are stretched across a bridge over a resonant box. The strings terminate on revolving pegs or posts on a headstock connected to the box. Each string is separately tuned to a note on an appropriate key by rotating the post to adjust the tension. In playing the instrument, the musician effectively alters the length of each string by pressing the string with a finger against a fret to shorten the string lengths and produce the vibrational frequency associated with the selected note.
The mechanism incorporated in the headstock to rotate each post and adjust string tension is referred to as a tuning machine. A finger operated tuning key is provided for each post and a gear mechanism of some type is provided to transmit the rotation of the key to the post. Typically the mechanism would be a worm gear arrangement, although in some instruments a planetary gear construction may be employed. These devices have mechanical advantages as high as 14 or 16 to one, so that the key has to be turned 14 or 16 complete revolutions to obtain one complete rotation of the post. For all practical purposes the mechanism is irreversible so that once the key is set to the desired tension of the string the string in theory should retain the tension.
However, in arrangements of the type just described, the strings are held in place on the posts by the accumulated friction of the string wound several times on the post with the end threaded through an opening, as illustrated in U.S. Pat. Nos. 490,564, 631,118, 778,128, 922,921, 2,173,800, and 3,240,098.
It is well known among musicians who play such instruments that the strings gradually lose some of their tension thus altering their pitch, and so must be returned at frequent intervals. Rough treatment of the strings can also result in their going out of tune. A major factor in the change of tension in such strings is due to wrapping of the ends of the strings around the posts, presumably due to slippage of the strings on the post overcoming the friction on which is relied to maintain the tension. That is, when the posts are rotated to adjust the strings to obtain the desired tension, there is a lag due to friction of the application of the tension over the portion of the string wrapped around the post. Over a period of time the tension of this portion of the string does adjust with the result that there is an alteration of the tension in the portion of the string stretched over the resonant box, resulting in the string becoming out of tune.
Prior attempts to clamp a string over less than one complete rotation on the post in order to avoid the use of winding have resulted in damage to the string and presented other problems, so that the multi-turned string on the post remains the predominant construction to terminate the string.